Posts Tagged 128k Plessey memory
My Nova 3’s 128kW Plessey Memory Board has another bit error – bit 7
Posted by Tommie in The Data General Nova 3 Restoration Project on Sunday 25 April, 2010
The Nova’s memory error indicates a flaky signal, but which signal? The error manifests itself on address 40000(oct), bit 7, but only running MEMDIAGLONG.ASM. Running MEMDIAGSHORT.ASM and MEMADDRTEST.ASM on the full 32kW works fine. MEMDIAGLONG runs fine up to the 16k boundary which would imply a faulty memory chip with a pattern sensitive problem, but manually loading memory generates a parity error in any location for bit 7, including the first 16k, which would indicate a faulty bus latch.
(MEMDIAGSHORT.ASM, MEMADDRTEST.ASM and MEMDIAGLONG.ASM are diagnostics by of 11/27/79 by T.P. Povlick that are loaded using the front panel switches.)
Nova 3 Plessey 128kW Memory Board with IC U146 16kx1 memory MK4116N-4 removed
The bit 7, address 40000 – 77777 (oct) error is now fixed by replacing the chip at row 2, column 7; IC U146. The 16kx1 memory IC is a MK4116N-4. (The Plessey board is 128kW consisting of 8 rows and 16 columns of 16kx1 chips.) Running MEMDIAGLONG.ASM on the full 32k now works fine. Since I currently have no floppy, disk or tape drive attached to the CPU, I am unable to run diagnostics on the full 128kW (256kB) address range.
I started the memory testing program MEMDIAGLONG at 13:50. The program runs 10 minutes per 1k of memory and was finished at 19:10 with no errors. Time running = 5h20m.
The 256kB Plessey Memory Board has a bit error
Posted by Tommie in Data General Minicomputer Projects, The Data General Nova 3 Restoration Project on Wednesday 10 March, 2010
128kb Plessey DG Nova 3 Memory Board
Bit 9 cannot be set after the machine has been running for 5 minutes or more. Clearly a thermal problem. Without the board schematics I will have to trace the MEM9 signal from the card edge connector inwards. Schematics would have been great! If you have the schematics for this board, a copy would be much appreciated.
The bit 9 error is now fixed; it was a faulty SN74S373 latch on the memory bus.
Data General Nova 3/12 Power Supply drawings
Posted by Tommie in Data General Minicomputer Projects, The Data General Nova 3 Restoration Project on Sunday 7 February, 2010
I have two Nova 3/12’s. One equipped with:
- NOVA 3 CPU, PWRFAIL, PRLOAD, 256KW
- NOVA 3 TRIPPLE OPT, MMPU, PAR, MUL/DIV, RTC
- 64KW Plessey, 128K SC, W PAR, 0-127
- DGC NOVA CASSETTE I/O, $TTI/O, 9600 B, RTC
- DISK CARTRIDGE CONTROL DGC NOVA, DKP, 4234, 6030
- DGC NOVA CASSETTE I/O, $TTI/O, 9600 B, RTC
The other is an empty chassis, both with faulty power supplies. I contacted Bruce Ray of Wild Hare Computer Systems and Bruce provided me with Nova 3/12 Power Supply and backplane drawings. I still have to troubleshoot and repair the power supplies, but at least I now have the drawings and the tools.
Picked up a Nova 3/12 from my friend Bjarni
Posted by Tommie in Data General Minicomputer Projects, The Data General Nova 3 Restoration Project on Monday 16 November, 2009
A fellow Data General minicomputer collector offered me his Nova 3/12 a while back and today me and friend went to his place to pick up the Nova 3. Bjarni, as the friendly guy he is, also offered me to take his Model 4234, Diablo drive which I did. I now have a DG 19” rack, the Nova 3/12 CPU with:
- NOVA 3 CPU, PWRFAIL, PRLOAD, 256KW
- NOVA 3 TRIPPLE OPT, MMPU, PAR, MUL/DIV, RTC
- 64KW Plessey, 128K SC, W PAR, 0-127
- DGC NOVA CASSETTE I/O, $TTI/O, 9600 B, RTC
- DISK CARTRIDGE CONTROL DGC NOVA, DKP, 4234, 6030
- DGC NOVA CASSETTE I/O, $TTI/O, 9600 B, RTC
- A 4234 Diablo disk drive and a 6026 Vacuum Tape Transport
I believe the Diablo disk drive was part of the Nova 3/12 system since it has a disk controller installed for the Diablo drive.